The overall goals of this project are to characterize cells of the murine system and determine the mechanism(s) of action and interactions among these cells in antibody responses to an antigen under immune response (Ir) gene control-L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT). T cells are critical for the development and regulation of immune responses; the understanding of the diversity and biological activity of T cell subsets is extensive, but little is known about T cell receptors for antigen or how regulatory T cells act. The objectives of this proposal are to identify and characterize regulatory T cell subsets in responder and nonresponder mice and (responder X nonresponder) F1 and (responder X responder)F1 mice after immunization with soluble GAT and GAT-macrophages. We have identified genetically restricted Lyt 1+, I-J- helper T cells, Lyt 1+, I-J+ suppressor-inducer and Lyt 2+, I-J+ suppressor effector T cells in (responder X nonresponder)F1 immunized with soluble GAT. Similar regulatory T cell subsets are in (responder X responder)F1 mice and are expected in parental responder and nonresponder mice. Our strategy is to establish cloned T cell lines representative of these regulatory T cell subsets and to characterize these clones by membrane antigen phenotype (Lyt 1, 2, 3; I-A; I-J; Qa 1; etc.), function and antigen-binding capacity. We plan to identify, isolate and characterize molecules in the membranes of these T cell clones which serve as recognition units or receptors for antigen and Ia restriction elements. New monoclonal serological reagents will be developed for this analysis by immunization with T cell clones. In addition, the mechanism(s) of action and interaction of the regulatory T cell clones will be determined to probe the cellular site and mechanism of expression of Ir gene function in antibody responses to GAT. These studies should lead to the identification of all essential T cell subsets involved in the regulation of antibody responses to one antigen under Ir gene control and provide insight into the nature of T cell receptors and the mechanism of Ir gene regulation of immunity.